Simplify the Expression $\sqrt [ 4 ] { \frac { 256 } { 81 } }$

Multiple Choice

Simplify the expression. Assume all variables represent positive real numbers.
- $\sqrt [ 4 ] { \frac { 256 } { 81 } }$

A) $\frac { 256 } { 81 }$
B) $\frac { 4 } { 3 }$
C) $\frac { 16 } { 9 }$
D) $\frac { 64 } { 27 }$